1. Field of the Invention
The present invention relates to the field of frequency multipliers.
2. Prior Art
Existing frequency triplers are square wave generators that have filtered outputs to select the third harmonic in the square wave output. The circuit consists of an oscillator generating a frequency f and a modulator which, switched at f, produces a train of odd order harmonics in decreasing amplitude:   "AutoLeftMatch"                              Z          =                      K            xc3x97                          SIGN              ⁡                              (                                  sin                  ⁢                                      xe2x80x83                                    ⁢                  ω                  ⁢                                      xe2x80x83                                    ⁢                  t                                )                                                                                              xe2x80x83                    ⁢                      =                          K              xc3x97                              4                π                            ⁢                              (                                                      sin                    ⁢                                          xe2x80x83                                        ⁢                    ω                    ⁢                                          xe2x80x83                                        ⁢                    t                                    +                                                            1                      3                                        ⁢                    sin                    ⁢                                          xe2x80x83                                        ⁢                    3                    ⁢                    ω                    ⁢                                          xe2x80x83                                        ⁢                    t                                    +                                                            1                      5                                        ⁢                    sin                    ⁢                                          xe2x80x83                                        ⁢                    5                    ⁢                    ω                    ⁢                                          xe2x80x83                                        ⁢                    t                                    +                  ⋯                                )                                                        
where: xcfx89=2xcfx80f
This technique has the disadvantage that the desired harmonic is nearly 10 dB below the fundamental signal, increasing the complexity of filtering required to select the third harmonic. Also, this approach results in extremely poor conversion efficiency, since over 90% of the signal power is wasted in undesired terms.
High efficiency, low noise frequency tripler and method that generates an enhanced third harmonic of a frequency and suppresses the fundamental frequency component in the tripler output. The method comprises multiplying a constant plus a twice frequency component by a square wave at the fundamental frequency, such as by a modulator. The amplitude of the twice frequency component relative to the constant and the phase of the twice frequency component relative to the phase of the square wave are chosen to reduce the fundamental frequency component and enhance the third harmonic in the tripler output. An implementation using a differential Colpitts oscillator is disclosed.